Electric induction apparatus



April 24, 1945. A. N. GARIN ELECTRIC INDUCTION APPARATUS Filed June 24, 1942 2 Sheets-Sheet l Inventor Alexis N. Gavin,

HIS Attorney.

April 24, 1945. A. N. GARIN 2,374,597

ELECTRI C INDUCT ION APPARATUS 'Filed June 24, 1942 2 Sheets-Sheet 2 Fig. 2.

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" physical symmetry 01 the apparatus.

Patented Apr. 24, 1945 fittl islitl ENDUQTEQN AFFAIR-AT US N. Garth, Pittsfield, Mess, assisiior to ileu emll Electric York @omsauy,

s cor ooretleh oi New ilgsgcllestlori .luhe $5 1, 1842, Serial No. l fifilll.

(Cl. Willi m?) My invention relates electric incluctiou apparatus, and although not limited thereto has particular application to split winding transformers.

In the design of electric induction apparatus, such as transformers 1mg a. plurality of wind ins-s, it is sometimes 1' .ssary to split one of the windings into r or circuits. Whenever this is done, ee u when the circuits are of the same voltage recurs, it is desirable that these circuits should possess symmetrical impede-rice characteristics, that is, the impedarices between any two circuits of the split winding should he approximately equal and the impedances between any circuit or the split Winding and the other winding should also be approximately equal. Physical symmetry in the arrsngement and location of circuits or" a split winding is the most con:- venient method of obtaining symmetrical impedonce characteristics. Thus, the usual way of obtaming symmetrical impedance characteristics is to have the number and location of the various circuits correspond with the physical symmetry of the apparatus. Split windings which include two circuits may have symmetrical impedance characteristics because of the two-way sy metry of typical normal transformer coustructioh Whether of core or shell type, cud with concentric or interleaved windings, since the two legs or a two-dragged design, or the two halves of a leg of a design having one leg per phase, either normally are, or can be madesymmetrical.

However, three, four, or five-Way physical symmetry required for split with three, four, ins may or may Winding transformers or five circuits in the split wind not he compatible with normal transformer construction. For instance, the twolegged, concentric, line-irr-the-micldle design has inherently two-Way symmetry and may have four way symmetry, but does not have three tvay or fiv e way symmetry. The three-group interleaved design has inherently two-Way symmetry and embodiment o may have three-way and six=way symmetry, but

does not have four-Way or five-tray symmetry.

It is, thereiore, an object of my invention to provide a structure which will have substantially symmetrical impedance characteristics for e. multiple circuit electric induction apparatus where the number of circuits does not correspond to the Another object of my invention is to provide an electric induction apparatus having three clr= cults in the secondary winding symmetricai tion has applies-tics matically lllustr the secondary e cult oi the structure the i have illustrator .icuit split t-Ji' uderstood the. to any other sultah induction s aps does not co yen symmetry the various tilt the three circu quadrants or l of each the .l. remainuig fourth our order to further ooh the impedance three circuits in the iour l are a posed with resrzect to each as to count any unsymmetrical relationship hetWe-c major portion of the circuits in the quadrants. uadrant or part or scale the core is considered as that portion whi hounded by two perpendicular planes each 3* c"- ing through the physical cen er of the core, one plane being in line with the lohgitudi al axis end the other plane being in line with the let rel axis. in the drawings the core, when it is assumed two perpendicular planes oses through the ohysiccl center, has lour physicelly similar certs or querirents or sections.

Referring more particularly to Fig. l or the drawings 1 have illustrated a transformer having it core member 50 with winding less it and it. Around the winding less ii and it are pieced primary Winding portions 53 and M, respectively, which may he the high voltage winding of the apparatus. Concentric with the winding M end in an upper part or upper quadrant of the appsi we (9 in es (0 number of coils.

ratus there is placed a winding or group L1. In the upper left hand quadrant of the apparatus and surrounding the winding leg H is placed a second winding circuit or group of windings L2, and surrounding the lower part of the winding leg IE or in a third quadrant is the third secondary winding circuit In. The winding sections L1, L2, and In may be the secondary or low voltage windings and they may have the same relative In order, therefore, to contribute to the symmetrical impedance characteristics of the low voltage windings having three circuits, a major portion of each of'the circuits is placed in some of the parts of the apparatus, such as in three or four quadrants or parts of the electric apparatus.

It is to be understood that the impedances between each of the windings L1, L2, and In are substantially symmetrical with respect to the adjacent portion of the high voltage windin s B3 and It by providing the geometrical mean distances of the major portion of the circuit with respect to the high voltage windings to be the same. The calculation of reactances by the geometrical mean distance is described in various publications, such as: Electricity and Magnetism-Clerk Maxwell-volume II (1873), Absolute Measurements in Electricity and Magnetism-A. Grayvol II (1893), On the G. M. D. of Rectangular Areas and the Calculation of Self- Inductance-E. B. Rosa, Bulletin of the Bureau of Standards-volume 3,.190'7.

together by a conductor 28 and which are placed on either side of the winding 13, the winding 12 being connected in series with the, winding L2. Winding 26 is connected to Liz by a conductor 29 and terminals 30 and M are provided for group 2.

Winding L3 is connected to la by a conductor 32 and terminals 33 and 3d are provided for group 3.

These three circuits, containing respectively, the coils (L1+l1), (L2-l-l2) and (La-H3), may have their terminals brought out independently of each other and may be connected to independent load circuits; or the terminals may be brought to a terminal board within the transformer for series or multiple connection to provide either a voltage or a current three times the capacity of one circuit as required; or again, the three circuits may be connected permanently either in series or in parallel. In the first case In order tocontribute further to the symmetrical impedance characteristics between the three low voltage winding circuits a portion of each of the circuits is placed in the remaining apparatus'parts or the fourth quadrant of the electric apparatus. As will be seen more clearly in the diagrammatic representation of Fig. 2, a portion of the first circuit, 11, is placed in the fourth quadrant and is connected in series with the L1 winding. Likewise a portion of the sec ond circuit is placed in the fourth quadrant in the form of a winding Z2, and Z3 is placed in the fourth quadrant in series with the L3 winding.

, Thus, the impedances between the three circuits and the adjacent high voltage windings will be substantially symmetrical- In order to provide for substantial symmetry of the impedance characteristics of the various secondary winding circuits to each other, the minor portions of each of the circuits, Z1, Z2 and 13, are disposed with respect to each other 'substan-' tially opposite to the relative relationships of the major portion L1, L2, L3. In other words desirable to place the minor portions of the windings, l1 and la, relatively far apart with respect to eachotherin the fourth quadrant. In order to accomplish this the minor portions of the winding 21 are formed into two windings 20 and 2| connected together by a conductor 22 and which are placed at the opposite ends of the quadrant relatively far apart from the windin Z3, which is centrally disposed with respect to the fourth quadrant. Winding 20 is connected to L1 by a conductor 23 and terminals 2c and 25 are provided for group 1.

* In like manner since L2 and La are relatively far apart, their minor portions Z2 and Z: are placed relatively close together in the fourth quadrant. However, in order that the minor portions will be symmetricalwith respect to each other, 12 is formed into two windings 26 and 21 connected 'since L1 and La are relatively close together it is above, the reactance relationship that is secured assures that the transformer will exhibit the same impedance characteristics, such as voltage reg ation or short-circuit current, with respect to each load circuit under similar conditions. In the second and third cases, if connected in series, the distribution of the leakage flux of the transformer will be symmetrical; and if connected in parallel, the division of load current among the three circuits will be equal.

The primary windings I3 and 14 may be formed in any suitable manner and in Fig. 2 I have shown four groups of coils, 35, 36, 31, and 38, one being in each quadrant. These four primary windings maybe connected in any suitable relationship, such as in parallel.

For best copper economy the general principle governing the distribution of total secondary turns between the major portion of the secondary winding (coils L1, L2, L3) and the remainder of the winding (coils Z1, Z2, Z3) is that with all, three, circuits of the secondary winding equally loaded, the secondary ampere turns in the four quadrants of the transformer should be substantially equal,

Ea h of those three circuits of the primary winding which is located in the quadrants conaining the L1, L2, L3 coils of the secondary winda g carries 3 X 110+ 3 X 28 of the primary line current; and the fourth circuit of the primary winding, located in the quadrant containing Z1, Z2, Z3 coils ofthe secondary winding, carries 22,374,597 number of circuits is difierent from the number of groups or parts which cru'respond to the physicalsymnietry of the apparatus, a {portion or a major portion of each of the winding circuits is placed on a, diiierent winding receiving section of the core, such different winding receiving sections typically comprising all but one of the total number of such sections, andall the minor portions of said windings being placed symmetrically with respect to each other on the remaining winding receiving section of the core.

It will be evident now that my invention provides means whereby a transformer winding may be split into' a desired number of electricallysymmetrical circuits when the structure of the transformer-does not lend itself to subdivision into an equal number of physical-symmetrical parts, and that the desired electrical symmetry can be secured with reasonable accuracy and very conveniently with the help of the physical symmetry characteristic. of the structure and involving a number of physical parts diiierent from the number of the electrical circuits, without the necessity of resorting to laborious inductance calculations, and sometimes even with a greater accuracy than could be secured by calculation with available inductance formulas without taking advantage of such physical symmetry.

Furthermore, it is evident that this same principle applies when the number of parts involved in the, physical symmetry difi'ers from the numbeiof circuits involved in the electrical symmetry by more than one.

Although I have shown and described a particular embodiment of my invention, my invention is not limited to the particular embodiment described; and I intend in the appended claims to cover all modifications which come within the spirit and scope ofmy invention.

What I claim as new and desire to secure by Letters Patent of the United States isr 1. In an electric induction apparatus having a core with two winding legs, first, second, and third windings adapted to form three circuits each of said windings portions connected respectively together, said major portion of said first winding surrounding approximately one-half of one of said legs, said major portion of said second winding surrounding approximately one-half of opposite said first winding major portion, said major portion of said third winding surrounding the remaining one-half of said first core leg, each of said minor portions of\said three windings surrounding the remaining one-half of said second core leg, said minor portion of said first winding having two subportions placed at op- 'ppsite ends of said second core leg remaining having major and minor said other leg I one-half, said minor portions of said second Winding having two subportions placed adjacent said subportionsof said first winding subportions,

and said mmoi' portion of said third winding being placed between said suhportions of said second minor winding portion.

2. A split winding transformer having at least two windings being subdivided into a. plurality of independent circuits having respective which are insulated'i'rom each othenand core means for per phase, one of said windings said windings having one more coil receiving section than said subdivided winding has circuits, all of said coil receiving core sections being excited by in-phase flux, said coil receiving core sections having physical symmetry, said circuits being disposed on said core means so that they have symmetrical impedance characteristics with respect to each other and with respect to the other of said windings by being subdivided respectively into major portions and minor portions, a major rportion or" each circuit being disposed on a different one or said coil receiving core sections, and all of said minor portions being disposed on the remaining coil receiving core section.

3. A split winding transformer having at least two windings per phase, one, of said windings being subdivided into a plurality of independent circuits having respective terminals which are insulated from each other, and unitary core means said circuits being disposed on said core means so that they have symmetrical impedance characteristics with respect to each other and with respect to the other of said windings by being subdivided respectively into major portions and minor portions, the major and minor portions of each circuit being serially connected, a major portion of each circuit being disposed on a differ'ent one of said coil receiving core sections,

"the impedance characteristics of said major por tions being unsymmetrical with respect to each other, and all of said minor portions being disposed on the remaining coil receiving core section, the physical relation between'said minor portions being such as to produce unsymmetrical impedance characteristics therebetween which are opposite to the unsymmetrical impedance characteristics between said major portions.

4. An electrical induction apparatus having a unitary core which is symmetrical about longitudinal and lateral axes ,so as'to .have four equal quadrants, a winding having three circuits each of which has a major portion and a minor portion, the major portions of each of said circuits being disposed respectively on threeof said quadrants, t e minor portions of each of said circuits bei disposed on the fourth quadrant so that sai circuits will have substantially symmetrical impedances with respect to each other.

5. An electrical induction apparatus having a unitary core which is symmetrical about longitudinal and lateral axes so as quadrants, a winding having three circuits each of which has a major portion and a minor portion, the major portions of said circuits being disposedflrespectively on three ofsaid quadrants, the minor portionsof said circuits being disposed on'the fourth quadrant, said minor port ons being disposed with respect to each other with relative distances diflerent from the relativedistances between said major portions so that said circuits will have substantially symmetrical impedances with respect to each other.

ALEXIS N. GARIN.

to have four equal 

